Contact mechanism



Dec? 1941- H. L. MEKELBURG arm, 2,265,567

conTAcT umcmmxsu Filed 001:. 14, 1940 2 Sheets-Sheet l Patented Dee-L a, 1941" oon'rsc'r MECHANISM' Harold L. Mekelburg, Milwaukee, and Carroll Stansbury, Wanwatosa. Wia. usignorl to Cutler-Hammer, Inc., Milwaukee, Wl l., a corporation of Delaware Application mm 14, an, Serial No. 361.124

.90laims.

andalth'ough not limited to such use the mechanism is particularly applicable to adjustable autotransformer or resistor type dimmers and the like. I

An object of the invention is to provide an improved contact mechanism which is relatively small or compact but has a relatively large capacity.

Another object of the invention is to provide a contact mechanism which has a low internal resistance.

Another object is to provide a contact brush mechanism which readily conducts the heat away from the brushes and dissipates it to the ambient air and to the supporting structure.-

Another object is to provide a brush mechanism (or. 200-171) This invention relates to a contact mechanism,

which engages the outer periphery of the auto-- Fla. 2 is a cross sectional view on the line 2-2 of Fig. l.

Fig. 3 is a fragmentary front view of the transformer shown in Figs. 1 and 2, with certain parts thereof removed for purposes of illustration. Fig. 4 is a top view of the brush mechanism of Fig. 4, and

Fig. 6 is a cross section along the line 8-6 of Fig. 3, showing the brush mechanism which comwhich has relatively large and efficient heat absorbing and radiating surfaces.

Another object is to provide a-brush mechanism in which the parts which have to adjust themselves to slight variations of the contact surface have a minimum of inertia so as to follow said variations instantly upon rapid relative movement.

Another object is to provide a brush mechanism which is easily removable as a unit, and the parts whereof are readily separable to facilitate replacement of the brushes.

Another object is to provide a brush mechanism in which the contact pressure varies little over a very wide range of brush movement due to wear and other causes.

Another object is to provide a brush mechanism in which the current is efliciently conducted from the movable brush to a relatively stationary part of the brush holder without the intervention of flexible conductors.

Another-object is to provide a brush mechanism the parts of which may be assembled as a unit prior to attachment thereof to the autotransformer dimmer or the like.

Other objects and advantages will hereinafter appear.

The accompanying drawings illustrate two embodiments of the invention.

In the drawings. Figure 1 is a side view of an autotransformer dimmer of the general type disclosed in our copending application, Serial No.

plates the electrical circuit from a fixed terminal to the rotating contact disc of the device.

Referring to Figs. 1, 2, 4 and 5, the brush mechanism shown therein is provided with a plurality of brushes l which are arranged substantially normal to and slidably engageable with the outer periphery of the autotransformer 2. The brushes are supported in a holder comprising an angle bracket 8 which is fastened to 'a rotatable contact disc or lever 4 by a screw 5 or other suitable means. The contact disc 4 is rotatable concentric with the center of the autotransformer dimmer and may be driven in any convenient way, as, for example (as shown in the aforementioned application). by a rotatable shaft 8 through an insulating coupling generally designated by the numeral 1. The free end of the bracket 3 is provided with an angular extension I to the further angled end of which is fastened a conducting and heat radiating block 8 of high electrical and heat conducting capacity which is preferably silver plated to provide it with a good conducting surface.

The block 9 has one end attached to the extension 8, as by means of a screw l0, and its other end is attached to the contact disc I, as by means of a screw ll. Supported in the extension 8 and in .the disc 4, respectively, are the two ends of a pivot pin l2, the reduced and shouldered end I8 of which is riveted to the extenof eachbell-crank is arranged to engage the out- 261,456, filed March 13, 1939 and assigned to the a same assignee, the dimmer herein disclosed, however, being provided with the contact brush mechanism which forms the subject matter of the present application.

er end of a brush 1, while the other arm of the bell-crank is provided near its end with a hole or eye I 5 through which passes a pin ii. The outer end of the pin it is provided with a head ll so as to limit its movement in the eye ii. The other end of the pin I6 is provided with a hemi spherical surface 18 which fits into a recess is in the brush i, said recess i9 being on the side of the brush opposite to that which makes contact with the block 9. A compression spring 20 surrounds the pin l8, one of its ends bearing against the bell-crank arm 2| while the other end is fastened in a groove 23 of the pin l6 near its hemispherical end so as to bias said arm 2| away from the brush and tending to rotate the bell-crank lever M in a clockwise direction as shown in Fig. 5. Due to the tendency of the lever M to rotate clockwise, the arm 22 which engages the end of the brush I exerts a radial pressure on the latter so as to press it firmly against the surface 2 to make contact therewith. As the brush l wears off the lever I4 gradually moves in a clockwise direction until the wear is sufficient to increase the distance between the arm 2| and the brush I to such an extent that the head i! engages the arm 2| thus stopping the spring-biased relative movement of the pin IS with respect to said arm. Likewise the free end of arm 2| will then be adapted to engage the bracket 3, whereby further movement of the brush toward the surface 2 is positively prevented. In practice, of course, the operator can determine when a brush or brushes require replacement by merely observing at intervals the positions of the arms 2| relatively to the bracket 3. In this manner proper engagement of all of the brushes with surface 2 can be assured, and disengagement of certain or all of the brushes from the surface 2 can be avoided.

It will furthermore be seen that if the complete assembly of brushes and brush holders shown in Figs. 4 and 5 is removed from the disc 5 by removing the screws 5 and I! said assembly is selfcontained and the brushes are held against complete ejection by engagement of the heads H with the arms 2| and engagement of the free ends of the latter with the bracket 3, thereby limiting the degree of clockwise movement of the levers M.

It will be further noted that the movable masses connected to and moving with each brush are very small and have-a low radius of gyration and therefore the brushes follow very readily and quickly any unevenness in the surface 2. Furthermore the centrifugal force exerted on the brushes l which tends to lift them off the surface 2 upon rotation of the lever 4 is relatively small and is to a large extent counteracted by the centrifugal force of the pin l6 and connected parts which tend to rotate the bell-crank l4 in a clockwise direction (Fig. 5).

The brush assembly shown in Figs. 3 and 6 is similar to that just described except that it is intended, as aforementioned, to conduct the current from the disc 4 to a stationary terminal. In this case the brushes are arranged in two rows at opposite sides of a central stationary contact block 30 which corresponds to the contact block 9 of Figs. 4 and 5. The brushes I are biased from their stationary supporting bracket toward rotatabledisc 2, and are therefore not subjected to any centrifugal force which tends to lift them off of the contact Surface of said disc. Except as pointed out. all essential details of the contact mechanism of Figs. 3 and 6 are similar to those aforedescribed and the brushes, bell-crank levers and springs are identical with those shown in Figs. 4 and 5. It will be observed that the current collected by the brushes and is carried to the contact blocks 9 and 30 respectively, in the most direct manner and on the shortest path. The same is true of the heat which may be developed in the contact brushes and surfaces aforementioned, so that the heat may be more readily dissipated to the ambient air and to the connected metal parts by said blocks.

It will also be observed that the relative'proportions and arrangement of each contact brush I, bell-crank lever l4 and spring 20 is such that upon wear of the brush and resulting reduction of spring pressure,the radial component of the pressure, exerted by the pin l6, increases relatively. This compensates partially for the reduction of radial pressure exerted upon the brush by the lever arm 22 due to the reduction of the torque exerted by the spring 20 upon the lever l4.

While we have herein illustrated a dimmer of the auto-transformer type, it will be obvious to those skilled in the art that the contact mechanism herein disclosed is likewise applicable to resistor type dimmers and the like.

As shown in Figs. 1 and 2 we prefer to attach to the inner surface of disc 4 a metal member 3| the weight of which is substantially equal to the weight of the multiple brush assembly shown in detail in Fig. 4. Member 3| is positionedupondisc 4 at a point 180 degrees removed from the assembly of brushes l-thus acting to counterbalance said assembly and thus equalize the amount of energy required to move the disc 4 through a given degree from each of the various rotary positions of the contact brush assembly. Theweight 3| also acts to neutralize any tendency of disc 6 to rotate under the influence of gravity in other than the lowermost and uppermost positions of the contact brushes with respect to surface 2.

We claim:

1. In combination, a contact brush adapted to engage a contact surface, a relatively stationary current and heat conducting block supporting said brush for sliding reciprocatory motion relatively thereto and substantially perpendicular to said surface, and spring biasing means, including means to urge said brush toward said surface and simultaneously against said block.

2. In combination, a contact brush adapted to engage a contact surface, a relatively stationary current and heat conducting block supporting said brush for sliding reciprocatory motion relatively thereto and substantially perpendicular to said surface, a bell-crank lever having one of its arms abutting said brush, and biasing means op-. erative betweenv the other arm of said lever and said brush to bias the latter towards said block and to rotate said lever to cause said one arm to urge said brush toward said surface.

3. The combination with a contact brush adapted to engage a contact surface, of a relatively stationary current and heat conducting block supporting said brush for sliding reciprocatory motion relatively thereto and substantially perpendicular to said surface, a bell-crank lever having one of its arms abutting one end of said to afford a contact surface, of a relatively stationary current and heat conducting block supporting said brush for sliding reciprocatory motion relatively thereto and substantially perpendicular to said surface, and spring biasing means,

including means to urge said brush toward said surface and simultaneously against said block.

5. In combination, a plurality of contact brushes adapted to engage a contact surface, a relatively stationary current and heat conduction block supporting said brushes in side by side relation for sliding reciprocatory motion relatively thereto and substantially perpendicular to said surface, a bell-crank lever for each one of said brushes having one of its arms abutting the respective brush, and biasing means operative between the other arm of said lever and said.

brush to bias the latter toward said block and to rotate said lever to cause said one arm to urge said brush toward said surface.

6. In combination, a contact brush adapted to engage a contact surface, a relatively stationary current and heat conducting block supporting said brush for sliding reciprocatory motion relatively thereto and substantially perpendicular to said surface, a bell-crank lever having one of its arms abutting said brush and its other arm provided with an eye near its end, a pin passing through said eye, one end of said pin being provided with a head to limit its movement through said eye in one direction and the other end of said pin being arranged to engage an abutment on said brush, and a helical spring surrounding said pin and having one of its ends abutting said other arm. and its other end attached to said pin to bias the latter toward said brush to thereby urge the latter toward said block and to rotate said lever to cause said one arm to urge said brush toward said contact surface.

"I. In combination, a contact brush adapted to engage a contact surface, a relatively stationary current and heat conducting block supporting said brush for sliding reciprocatory motion relatively thereto and substantially perpendicular to said surface, a bell-crank lever having one of its arms abutting said brush and its other arm provided with an eye near its end, a pin passing through said eye, one end of said pin being provided with a head to limit its movement through said eye in one direction and the other end of said pin being arranged to engage an abutment on said brush, a helical spring surrounding said pin and having one of its ends abutting said other arm and its other end attached to said pin to bias the latter toward said brush to thereby bias the latter toward said block and to rotate said lever to cause said one arm to urge said brush toward said contact surface, and a relatively stationary abutment arranged in the path of said other arm to limit the rotation thereof under the influence of said biasing spring.

8. The combination with a plurality of contact brushes for a variable rheostat or the like adapted to slide over a plurality of contacts arranged side by side to afford a contact surface, of a relatively stationary current and heat conducting block supporting said brushes for sliding reciprocatory motion relatively thereto and substantially perpendicular to said surface, a bellcrank lever for each one of said brushes having one of its arms abutting the respective brush and its other arm provided with an eye near its end, a pin passing through said eye, one end of said pin being provided with a head to limit its movement through said eye in one direction and the other end of said pin being arranged to engage an abutment on said brush, a helical spring surrounding said pin and having one of its ends abutting said other arm and its other end attached to saidpin to bias the latter toward the respective brush to thereby bias the latter toward said block and to rotate said lever to cause said one arm to urge said'brush toward said contact surface, and a relatively stationary abutment arranged in the path of said other arm to limit the rotation thereof under the influence of said biasing spring.

9. As an article of manufacture, a contact brush assembly comprising a metal bracket adapted for attachment to a suitable support, a current and heat conducting metal member rigidly attached to said bracket, a pivot pin rigidly attached to said bracket in laterally spaced relation to said metal member, a bell-crank lever freely slidable onto said pin for pivotal support thereby, a headed pin the'shank of which is slidably supportedby one arm of said bell-crank lever, said shank having a shoulder formed thereon, a coiled compression spring interposed between said shoulder and said lever arm, a contact brush having a recess formed therein to accommodate the end of said pin shank, the other arm of said bell-crank lever being engaged with said brush at a predetermined distance from said recess, said last mentioned pin acting to press said brush against said metal member and said last mentioned lever arm acting to bias said brush for sliding movement thereof in a given direction relatively to said metal member, and means for limiting the degree of pivotal movement of said bell-crank lever in one direction to correspondingly limit the degree of sliding movement of said brush, whereby all of said parts are retained in assembled relation.

HAROLD L. MEKELBURG. CARROLL STANSBURY. 

